Pourable,storable polymerizable lactam-catalyst-activator mixtures

ABSTRACT

A POURABLE, STORABLE, POLYMERIZABLE LACTAM-CATALYST-ACTIVATOR MIXTURE COMPRISING AT LEAST ONE LACTAM HAVING MORE THAN 5 RING MEMBERS, AT LEAST ONE ALKALINE CATALYST AND AT LEAST ONE ACTIVATOR BEING EMBEDDED IN AN ORGANIC MATERIAL.

United States Patent US. Cl. 26018 N 8 Claims ABSTRACT OF THE DISCLOSUREA pourable, storable, polymerizable lactam-catalyst-activator mixturecomprising at least one lactam having more than 5 ring members, at leastone alkaline catalyst and at least one activator being embedded in anorganic material.

This invention relates to pourable, storable polymerizablelactam-catalyst-activator mixtures which contain one or more activatorsembedded in hydrophobic organic material.

It is known that lactams, such as e-CflPIOlZlCiflIIl, caprylic lactam orlauric lactam, can be polymerized to form polyamides by activatedanionic polymerization carried out in the presence of a basic catalystand an activator.

Catalysts for the activated polymerization of lactams include alkalimetal and alkaline earth metal compounds of lactams, for example sodiume-caprolactamate; or of carboxylic acids having 1 to 6 carbon atoms, forexample potassium formate; or of alcohols having up to 6 carbon atoms,for example sodium methoxide, potassium t-butoxide or sodium phenoxide;or alkali metal and alkaline earth metal hydrides, hydroxides andcarbonates.

The activators used include, for example, isocyanates, such ashex-amethylene1,6-diis0cyanate or phenyl isocyanate, or maskedisocyanates such as hexamethylene-1,6- bis-(carbamido caprolactams),ketones, carbodiimides, acid chlorides, carboxylic acid esters,carboxylic acid imides, and triazines.

Mixtures of such lactams, catalysts and activators commonly used foractivated anionic lactam polymerization are not stable on storage evenif kept at room temperature with the exclusion of air and moisture.After a relatively short time they are incapable of being polymerized.It is very important to find a mixture which is stable on storage forsimplifying the mixing of the components, transport, keeping reservestocks and working up.

Lactam-catalyst-activator mixtures which are stable on storage attemperatures below 50 C. have been described in Germanolfenlegungsschrift No. 1,570,403. They are prepared by using so-calledlatent catalysts which de compose into the reactive catalyst itself onlyat elevated temperatures of about 140 C. or more with the evolution ofCO These mixtures have the disadvantage that the polyamide producedcontains bubbles caused by the evolution of CO So-called one componentcatalysts, i.e. compounds which act both as activators and as catalysts,have also been described as forming storable polymerizable mixtures withlactams. These compounds are alkali metal compounds of amides andanilides, e.g. of N,N-dimethylurea, urethanes, acylated hydroxamic acidsor caprolac tam-N-carboxylic acid anilides (French patent specificationNo. 1,553,382) or alkali metal salts of int-substituted B-ketoamides(German oifenlegungsschrift No. 1,595,454 and French patentspecification No. 1,544,070). These compounds have two disadvantages:firstly they are expensive to produce, and secondly they show littleactivator reactivity which necessitates long operating cycles for staticcasting, spray casting and rotary casting.

In addition, British patent specifications No. 928,313 and 928,314describe lactam-catalyst mixtures, i.e. twocomponent mixtures, in whichthe catalyst is embedded in lactam tablets. Apart from the fact that theprocess by which they are produced is extremely expensive, mixtures ofthis kind are not sufliciently pourable and show a marked tendencytowards disintegration into their components.

It has now surprisingly been found that a pourable, storable,polymerizable lactam-catalyst-activator mixture can be obtained byembedding the activator in hydrophobic 4 organic material.

Accordingly, the invention relates to a pourable, storable,polymerizable lactam-catalyst-activator mixture comprising at least onelactam having more than 5 ring members, at least one alkaline catalystand at least one activator being embedded in an organic material whichcontains at least one hydrophobic radical and which loses its barriereffect under the conditions of anionic polymerization, by melting ordissolving in the lactam melt.

The lactam-catalyst-activator mixtures preferably contain the activatoror an activators mixture embedded in a protective material which issolid at a temperature below 50 C. In principle, the embedded activatorin the mixture may be any activator that is suitable for the anionicactivated polymerization of lactams, for example isocyanates such asphenyl isocyanate, tolylene-l,4-diisocyanate,hexamethylene-1,6-diisocyanate, masked isocyanates such ascaprolactam-N-carboxylic acid-N'-phenylamide, carbodiimides such ashexamethylene-l,6-bis-(carbamidocaprolactam), triazines such astriphenoxy-s-triazine, N-acyllactams such as N-stearoyl-caprolactam.

Suitable embedding materials include wax-like compounds having meltingpoints above 50 C. and which lose their barrier effect at thepolymerization temperature, i.e. at temperatures of from to 250 C. bymelting or dissolving in the lactam melt. The wax-like compounds containin the molecule at least one hydrophobic radical having preferably atleast 10 carbon atoms. Hydrophobic radicals such as these include, forexample,

linear or branched parafiin chains, optionally interrupted orsubstituted by aromatic or 'alicyclic groups or aliphatic, condensedring systems. In principle, there is no upper limit to the number ofcarbon atoms in the molecule, because oligomeric and polymeric compoundsare also suitable, providing they can be used in an embedding orencapsulating process and satisfy the above mentioned requirements.

The following are given as examples of such embedding materials:aliphatic hydrocarbons such as paraflins, e.g. hard parafiins,polyolefines, e.g. low molecular weight (high density) and highmolecular weight (low density) polyethylenes and polystyrenes, fattyalcohols having 10 to 30 carbon atoms, e.g. stearyl alcohol, esters offatty acids having 10 to 30 carbon atoms such as stearic acidp-nonyl-phenolate and cholanic acid butyl ester but also waxes and fatsof natural or synthetic origin such as beeswax or beef tallow, amidesand imides of fatty acids having 10 to 30 carbon atoms, e.g. N-stearylphthalimide, behenic acid cyclohexylamide, stearic acid cyclohexylamideor acetic acid stearylamide; ketones having 10 to 30 carbon atoms suchas stearone or civetone. Compounds which have other functions inaddition to their function as protective material are particularlysuitable for example long chained fatty alcohols and amides which alsofunction as molecular weight regulating agents in the polymerization oflactams. Many of the compounds mentioned above also act as mould partingagents. Stearic acid cyclohexylamide is especially suitable. Mixtures ofthe above mentioned embedding materials may also be used.

Embedding can be effected for example, by spray drying, fluidized-bedcoating, electrostatic spraying, coacervation, precipitating polymersfrom their solutions, and phase-interface (in situ) polymerization.

Effective embedding may also be achieved by mixing the activator withthe embedding compound, melting the mixture and cooling the melt by anysuitable method, leaving it to solidify and then size reducing it, e.g.by scaling it over a cooling roller. The pourable stable, polymerizablemixture is obtained by adding the lactam and the catalyst.

Liquid activators can also be converted into a pourable powder ormicrogranul-ate by the above mentioned embedding processes, and can inthis way be made suitable for use in pourable lactam-catalyst-activatormixtures.

Both the grain size and the quantities ratio between the embedded andthe embedding material can be varied in the aforementioned processes.The embedding material can be used in an amount of from 1 to 500% byweight, preferably in an amount of from 10 to 200% by weight, based onthe material to be embedded.

The embedded activators can be used in an amount of from 0.1 to 20 molpercent preferably in an amount of from 1 to 10 mol percent ofactivator, based on the quantity of polymerizable lactam.

Lactams which have more than 5 ring members, e.g. fl-pyrrolidone,e-caprolactam, oenantholactam, caprylolactam or lauric lactam aresuitable for preparing the stable pout-able mixtures according to theinvention.

Any catalyst for the activated anionic polymerization of lactams, e.g.alkali metal and alkaline earth metal compounds of lactams such assodium e-caprolactamate or of aliphatic carboxylic acids having 1 to 6carbon atoms such as sodium formate or potassium formate or of alcoholshaving up to 6 carbon atoms such as sodium methylate, potassium tertiarybutylate or sodium phenolate or alkali metal and alkaline earth metalhydrides, hydroxides, carbonates may be used.

The catalyst is added in quantities from 0.1 to 20, preferably 1 to 10mols percent based on the lactam to be polymerized.

The overall mixture can be prepared in the conventional manner by mixingthe three components, i.e. lactam, catalyst and embedded activator, at atemperature below 50 C. in the absence of moisture. It is also possible,however, to dissolve the catalyst in a molten lactam, to cool the melt,for example by means of a cooling roller, after which it is flaked oitand subsequently added 1 to the embedded activator used according, tothe invention.

Additives can also be introduced into these mixtures, either at theoutset or before, during or after polymerization. Examples of theseadditives include regulators such as butyl acetamide; organic orinorganic pigments or dyes such as carbon black, titanium dioxide orphthalocyanines; plasticizers or mould-release agents; organic orinorganic fibres such as glass fibres or mats or fibrous asbestos;fillers such as glass balls, calcium carbonate or bentonite;flame-proofing agents such as red phosphorus, organic halogen compounds,phosphoric acid esters or metal oxides; blowing agents such as azides orhydrocarbons; and, finally, polymers as well, for example groundpolycaprolactam waste, nylon 66 or polystyrene.

The mixtures according to the invention are stored in a scaled containerwith the exclusion of moisture. Surprisingly they are stable for weeksnot only in a nitrogen atmosphere but also in air. They can bepolymerized with undiminished activity even after 6 Weeks.

In view of the extreme sensitivity of anionically polymerizable systems,it must be regarded as extremely surprising that the polymerizability ofthe mixtures according to the invention is in no way adversely aifectedby the embedding materials nor even by being stored in air.

On the contrary, these mixtures can readily be polymerized in theconventional manner at temperatures of from 140 to 300 C. Polymerizationcan be carried out either as a batch process, for example by gravitycasting or by rotational casting, although it is best carried outcontinuously, for example in an injection-moulding apparatus, in a screwpress or ram extruder, the polymerizable mixture being optionally fusedin a preceding vessel and delivered by means of a gear pump into theheated barrel of the apparatus used.

Accordingly, the invention also relates to a process for the productionof polyamides by the anionic polymerization of lactams having more than5 ring members wherein the lactam is polymerized at a temperature offrom 140 to 300 C. in the presence of an activator embedded in anorganic material containing at least one hydrophobic radical and beingsolid at room temperature, and an alkaline catalyst.

The polymerization time and also the conversion rate, expressed by theextract content of the polyamide formed, serve as a measure of thestorage stability of the mixtures according to the invention.

EXAMPLE I A mixture of 1150 g. ofhexamethylene-1,6-bis-(carbamidocaprolactam) and 1000 g. of stearic acidcyclohexylamide is melted under nitrogen. The resulting melt isthoroughly mixed, and then flaked onto a cooling roller to givecolorless flakes melting at 75 to 77 C.

Several 100 mL-flasks with ground-glass stoppers are each filled with56.6 g. of e-caprolactam, 0.3 g. of 85% by weight sodium caprolactamatein caprolactam and 1.12 g. of the embedded catalyst prepared asdescribed above and tightly closed with a ground-glass stopper. Thecontents of the bottles are thoroughly mixed by shaking and then stored.After intervals of 0, 11, 20, 39, 60 and days, respectively one of theflasks is placed in a stirring apparatus immersed in an oil bath heatedto 210 C. and its content is polymerized. The polymerization time is thetime elapsing from immersion of the flask the point in time at which thepolyamide formed can no longer be stirred. The polyamide is then heatedfor another 30 minutes at 210 C. and cooled.

EXAMPLE 2 dure is as described in Example 1. The following results areobtained.

Polym- Storage erization time time Flask (days) (minutes) EXAMPLE 3 100g. of hexamethylene-1,6-bis-(carbamido-caprolactam) and 100 g. ofbehenic acid cyclohexylamide are fused under nitrogen. The clear meltcan be solidified in a mortar and powdered.

Samples are prepared as in Example 1 using 1 g. of this embeddedactivator but the flasks are purged three times by evacuation andeliminating the vacuum with nitrogen and then tightly sealed with aground-glass stopper, and then stored in a drying chest at 50 C.Polymerization is carried out in the same way as described in Example 1.

Polym- Storage erization time time Flask (days) (minutes) EXAMPLE 4 30kg. of behenic acid cyclohexylamide, 70 kg. ofhexamethylene-1,-6-bis-(carbamido-caprolactam) and '60 kg. of glycolmonomethyl ether are heated at 70 to 75 C. to form a clear melt. Thismelt is extruded into 300 litres of water kept at 60 C. Followingremoval from the precipitation bath, a spherical product is formed, andis freed from adhering water in a shelf dryer at 45 C./0.1 to 50 torr.

Several 100 ml. ground-glass flasks are each filled with 56 g. (0.5 mol)of e-caprolactam, 0.3 g. of 66% by weight sodium e-caprolactamate incaprolactam and 1.2 g. of the embedded activator described above. Theflasks are purged three times by evacuation and eliminating the vacuumwith nitrogen and then tightly scaled with a groundglass stopper. Thepolymerization is carried out as described in Example 1. After coolingthe polyamide is sawn chopped and extracted for 12 hours with methanol.

Polym- Extract Storage erizetion content time time (percent by (days)(minutes) weight) EXAMPLE 5 EXAMPLE 6 Mixtures similar to those ofExample 5 are prepared, except that, as activator, they each contain 1g. of hexamethylene 1,6 bis- (carbamido-caprolactam) embedded 1:1beeswax. The mixtures are polymerized and worked up as in Example 4.

Mixtures similar to those of Example 5 are prepared, caprolactam)embedded 1:1 in hard parafiin. The mixtures are polymerized and workedup as described in Example 4.

Polym- Extract Storage erization content time time (percent by Flask(days) (minutes) weight) What is claimed is:

1. A pourable, polymerizable lactam-catalyst-activator compositioncomprising at least one lactam having more than 5 ring members, at leastone activator in an amount of from 0.1 to 20 mol percent, based on thequantity of said lactam present, and a catalytic amount of at least onealkaline catalyst, said activator being embedded within 1 to 500% byweight, based on the weight of said activator, of a wax-like compoundhaving a melting point above 50 C. and containing in the molecule atleast one hydrophobic radical having at least 10 carbon atoms and losingits barrier effect under the conditions of anionic polymerization bymelting or dissolving in the lactam melt, whereby said embeddedactivator is isolated from said lactam and said catalyst prior topolymerization.

2. A mixture as claimed in claim 1, wherein the embedding material isparaflin, polyolefin, fatty alcohol having 10 to 30 carbon atoms, ester,amide or imide of a fatty acid having 10 to 30 carbon atoms, a wax orfat of natural or synthetic origin or ketone having 10 to 30 carbonatoms.

3. A mixture as claimed in claim 1, wherein the embedding material ishard paraflin, low molecular weight or high molecular weightpolyethylene, polystyrene, stearyl alcohol, stearic acid,p-nonyl-phenolate, cholanic acidbutyl ester, beeswax, beef tallow,Nstearyl phthalimide, behenic acid cyclohexylamide, stearic acidcyclohexyl amide, acetic acid stearylamide, steanone or civetone.

4. A mixture as claimed in claim 1, wherein the lactam component isB-pyrrolidone, ecaprolactam, oenantholactam, caprylolactam, or lauriclactam.

5. A mixture as claimed in claim 1, wherein as activator an isocyanate,masked isocyanate, carbodiimide, triazine or N-acyllactam is used.

6. A mixture as claimed in claim 1, wherein as activator phenylisocyanate, tolylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate,caprolactam-N-carboxylic acid-N- phenylamide,hexamethylene-1,6-bis-(carbamidocaprolactang), triphenoxy-s-triazine orN-stearoyl-caprolactam, is use 7. A mixture as claimed in claim 1,wherein as catalyst an alkali metal or alkaline earth metal compound ofa lactam of an aliphatic carboxylic acid having 1 to 6 carbon atoms orof an alcohol having up to 6 carbon atoms is used.

8. A mixture as claimed in claim 1, wherein as catalyst sodiume-caprolactamate, sodium formate, potassium formate, sodium methylate,potassium tert.-butylate or sodium phenolate is used.

(References on following page) References Cited UNITED STATES PATENTSMarshall et a1. 260-78 Hill et a1. 260-78 Hermann et a1. 260-78 Hermannet a1. 260-78 Tokiura et a1. 260-857 Brignac 260-28 Birkner 260-78Darnell et al 260-78 Sahler 260-78 8 FOREIGN PATENTS 928,313 6/1963Great Britain 260-78 928,314 6/1963 Great Bn'tain 260-78 5 DONALD E.CZAIA, Primary Examiner E. C. RZUCIDLO, Assistant Examiner US. Cl. X.R.

10 260-28, 31.2 N, 32.4 R, 32.6 N, 32.8 N, 33.4 R, 33.6 R,

78 L, 857 UN; 264-300

